Hello, VishalJani.
The fact that you turn on the Automatic Document Feeder. By default the XferCount is equal to infinity. Therefore, the only way for the scanner to report the end of the scan - this is to inform you that a user canceled the scanning (in a Twain32.AcquireError
instead a Twain32.AcquiredCompleted).
Try process AcquireError event.